Accuracy of Stress Radiography Techniques in Grading Isolated and Combined Posterior Knee Injuries

Abstract

Background Stress radiography techniques have been shown to be superior to the arthrometer and clinical examination in evaluating the posterior cruciate ligament—deficient knee, but no precise relationship has been established between the extent of the lesion and the laxity measured by stress radiography. Hypothesis It is possible to establish a precise relation between posterior laxity and the anatomical lesions of the posterior cruciate ligament and posterior structures using stress radiography. Study Design Controlled laboratory study. Methods Measurements were performed on 15 fresh-frozen cadaveric knee specimens. A partial posterior cruciate ligament lesion was created by sectioning the anterolateral bundle, followed by a complete section. Then the lateral collateral ligament and the posterolateral corner were transected, and finally the medial collateral ligament and the posteromedial corner were sectioned. Stress radiography was performed first on the intact knee and again after each lesion was created using 4 techniques: Gravity Sag View, PCL-Press, Telos at 80°, and Telos at 30° of flexion. Results Telos 30 and Telos 80 revealed the best overall performance as a diagnostic test in terms of accuracy in discriminating between the different types of lesions. Using the Telos device, we determined the following cut-off points: for a partial lesion, less than 3 mm at 30° and less than 6 mm at 80°; for a complete lesion, between 4 mm and 9 mm at 30° and between 7 mm and 12 mm at 80°; for associated peripheral lesions, more than 9 mm at 30° and more than 12 mm at 80°. Conclusion The Telos 30° and 80° allow us to accurately distinguish between the different types of lesion and permit grading of posterior knee laxity. Clinical Relevance Stress radiography allows characterization of posterior knee injuries and helps to determine treatment strategy.